Flat-panel display devices are widely used in conjunction with computing devices, in portable devices, and for entertainment devices such as televisions. Such displays typically employ a plurality of pixels distributed over a substrate to display images. Each pixel incorporates several, differently colored light-emitting elements commonly referred to as sub-pixels, typically emitting red, green, and blue light, to represent each image element. Pixels and sub-pixels are not distinguished herein; all light-emitting elements are called pixels. A variety of flat-panel display technologies are known, for example plasma displays, liquid crystal displays, and light-emitting diode displays.
Flat-panel display devices can be used in video communication systems. Typical commercially available systems employ a display together with an imaging device, such as a digital camera, located above or below the center of the display that communicates with a similar, remote system. Each imaging device makes an image of a person seated in front of the display. A microphone simultaneously records speech. The image and speech are sent, e.g. via the internet, computer network, or telephone network, to the remote system where the image is displayed and the speech is rendered on a speaker. In this way, two (or more) individuals can see each other on a pair of displays at the same time and communicate with each other visually and aurally from separate locations, which are remote from each other. Such video interaction enhances the communication.
It is desirable in video communication systems to have the imaging device located at the point at which the individual gazes, thus giving the impression of eye contact. This is difficult, however, since a communicating individual will tend to look at the display while addressing the remote individual, thus giving the appearance that the individual is not looking at the person to whom he or she is speaking
This problem is addressed, for example in commonly-assigned US 2008/0106628 and US 2008/0106629 by providing a transparent opening in a display and locating one or more digital cameras behind the display so that an individual whose gaze is directed at the display will also gaze toward at least one camera giving the impression of eye contact with the remote individual.
Similarly, U.S. Pat. No. 7,034,866 describes a combined display-camera with interspersed display and camera elements. U.S. Pat. No. 5,340,978 describes an LCD panel and solid-state image sensor. U.S. Pat. No. 7,535,468 discloses an integrated sensing display with display elements integrated with image sensing elements. US 2009/0146967 discloses a display apparatus including a display section; a light radiating section; a plurality of light converging lenses; and a plurality of light-receiving elements. WO 2004/107301 discloses microlenses intermixed with display pixels.
In these various disclosures, the image sensors are typically located behind the display, forming a relatively thick, integrated structure with multiple, separate elements that must be assembled into a relatively complex structure. In some cases, the digital cameras employed are relatively thick to provide a suitably long optical axis providing higher-quality imaging. In other cases, a lens element is located very close to, or on, an imaging element which can deteriorate the quality of the images captured. In other cases, relatively few image sensing elements are provided, reducing the resolution of the formed images. Hence, prior art image capture and display systems typically suffer from reduced image quality (e.g. resolution and sharpness) or are thicker than can be desirable.
Light-emitting diodes (LEDs) incorporating thin films of light-emitting materials forming light-emitting elements have many advantages in a flat-panel display device and are useful in optical systems. For example, organic LED color displays include arrays of organic LED light-emitting elements. Alternatively, inorganic materials can be employed and can include phosphorescent crystals or quantum dots in a polycrystalline semiconductor matrix. Other thin films of organic or inorganic materials can also be employed to control charge injection, transport, or blocking to the light-emitting-thin-film materials, and are known in the art. The materials are placed upon a substrate between electrodes, with an encapsulating cover layer or plate. Light is emitted from a pixel when current passes through the light-emitting material. The frequency of the emitted light is dependent on the nature of the material used. In such a display, light can be emitted through the substrate (a bottom emitter) or through the encapsulating cover (a top emitter), or both.
LED devices can include a patterned light-emissive layer wherein different materials are employed in the pattern to emit different colors of light when current passes through the materials. Alternatively, one can employ a single emissive layer, for example, a white-light emitter, together with color filters for forming a full-color display. It is also known to employ a white sub-pixel that does not include a color filter. A design employing an un-patterned white emitter has been proposed together with a four-color pixel comprising red, green, and blue color filters and sub-pixels and an unfiltered white sub-pixel to improve the efficiency of the device.
Two different methods for controlling the pixels in a flat-panel display device are generally known: active-matrix control and passive-matrix control. In an active-matrix device, control elements are distributed over the flat-panel substrate. Typically, each sub-pixel is controlled by one control element and each control element includes at least one transistor. For example, in a simple active-matrix organic light-emitting (OLED) display, each control element includes two transistors (a select transistor and a power transistor) and one capacitor for storing a charge specifying the brightness of the sub-pixel. Each light-emitting element typically employs an independent control electrode and a common electrode.
Prior-art active-matrix control elements typically comprise thin-film semiconductor materials, such as silicon, formed into transistors and capacitors through photolithographic processes. The thin-film silicon can be either amorphous or polycrystalline. Thin-film transistors made from amorphous or polycrystalline silicon are relatively larger and have lower performance than conventional transistors made from crystalline silicon wafers. Moreover, such thin-film devices typically exhibit local or large-area non-uniformity that results in perceptible non-uniformity in a display employing such materials. While improvements in manufacturing and materials processes are made, the manufacturing processes are expensive and thin-film device performance continues to be lower than the performance of crystalline silicon devices.
Matsumura et al discuss crystalline silicon substrates used with LCD displays in US 2006/0055864. Matsumura describes a method for selectively transferring and affixing pixel-control devices made from first semiconductor substrates onto a second planar display substrate. Wiring interconnections within the pixel-control device and connections from busses and control electrodes to the pixel-control device are shown. The article “A hemispherical electronic eye camera based on compressible silicon optoelectronics” in “Nature” vol. 454 August 2008 p. 748 describes a high-performance, hemispherical electronic eye camera based on single-crystalline silicon. These disclosures, however, do not provide an integrated image capture and display apparatus.
WO2010046643 describes an optical sensor that uses chiplets.
There is a need, therefore, for improving the performance of an integrated image capture and display apparatus incorporating active-matrix light-emissive elements in a compact and robust structure having improved imaging performance.